Underrepresentation of black individuals in pivotal trials for novel anticancer drugs: Potential consequence of using estimated creatinine clearance to assess kidney function?

Background: Black individuals are historically underrepresented in oncology clinical trials. One potential reason for this is the prevalence of kidney disease in Black individuals, utilization of estimated creatinine clearance as a surrogate for glomerular filtration rate (GFR) in oncology, and GFR-based trial eligibility criteria. We characterized the representation of racial minorities in anticancer agent pivotal trials and examined if GFR-based trial eligibility criteria impact the proportion of Black individuals in trial populations.

Methods: We constructed a data repository for anticancer drugs FDA-approved from 2015 to 2019 and associated pivotal trials, from which we extracted trial population racial compositions and GFR-based trial eligibility criteria. We calculated the participation-to-incidence ratio (PIR) and participation-to-mortality ratio (PMR) for a variety of cancer sites, where PIR or PMR >1.2 and <0.8 indicate overrepresentation and underrepresentation, respectively. We evaluated the relationship between GFR eligibility cutoffs and the proportion of Black enrollees with Spearman rank correlation coefficient.

Results: We assessed 24,698 patients in 74 trials. Black individuals were underrepresented in all trials (PIR ≤0.48, PMR ≤0.50). For trials with GFR-based eligibility criteria (n = 49), a lower GFR cutoff was modestly associated with a higher proportion of Black enrollees (r = -0.29, p = 0.039). This relationship was strengthened for trials that only used estimated creatinine clearance to estimate GFR (r = -0.43, p = 0.004).

Conclusions: GFR-related eligibility, and specifically the use of estimated creatinine clearance, may contribute to Black individuals being disproportionately excluded from cancer clinical trials. This highlights the need for implementation of contemporary GFR equations and other interventions to boost racial minority trial enrollment.